The Impact of Postoperative Tumor Burden on Patients With Brain Metastases

Background: Brain metastases were considered to be well-defined lesions, but recent research points to infiltrating behavior. Impact of postoperative residual tumor burden (RTB) and extent of resection are still not defined enough. Patients and Methods: Adult patients with surgery of brain metastases between April 2007 and January 2020 were analyzed. Early postoperative MRI (<72 h) was used to segment RTB. Survival analysis was performed and cutoff values for RTB were revealed. Separate (subgroup) analyses regarding postoperative radiotherapy, age, and histopathological entities were performed. Results: A total of 704 patients were included. Complete cytoreduction was achieved in 487/704 (69.2%) patients, median preoperative tumor burden was 12.4 cm³ (IQR 5.2–25.8 cm³), median RTB was 0.14 cm³ (IQR 0.0–2.05 cm³), and median postoperative tumor volume of the targeted BM was 0.0 cm³ (IQR 0.0–0.1 cm³). Median overall survival was 6 months (IQR 2–18). In multivariate analysis, preoperative KPSS (HR 0.981982, 95% CI, 0.9761–0.9873, p < 0.001), age (HR 1.012363; 95% CI, 1.0043–1.0205, p = 0.0026), and preoperative (HR 1.004906; 95% CI, 1.0003–1.0095, p = 0.00362) and postoperative tumor burden (HR 1.017983; 95% CI; 1.0058–1.0303, p = 0.0036) were significant. Maximally selected log rank statistics showed a significant cutoff for RTB of 1.78 cm³ (p = 0.0022) for all and 0.28 cm³ (p = 0.0047) for targeted metastasis and cutoff for the age of 67 years (p < 0.001). (Stereotactic) Radiotherapy had a significant impact on survival (p < 0.001). Conclusions: RTB is a strong predictor for survival. Maximal cytoreduction, as confirmed by postoperative MRI, should be achieved whenever possible, regardless of type of postoperative radiotherapy.